AAT
Normal plasma concentration of alpha-1 antitrypsin (AAT) ranges from 1.3 to 3.5 mg/ml. Under certain conditions, AAT easily diffuses into tissue spaces and forms a 1:1 complex with target proteases, principally neutrophil elastase. Other enzymes such as trypsin, chymotrypsin, cathepsin G, plasmin, thrombin, tissue kallikrein, and factor Xa can also serve as substrates. The enzyme/inhibitor complex is then removed from circulation by binding to serpin-enzyme complex (SEC) receptor and catabolized by the liver and spleen.